Tamper for concrete road finishing machines



May 26, 1936. H. M CRERY 2,042,156

TAMPER FOR CONCRETE ROAD FINISHING MACHINES Filed Dec. 29, 1933 4 Sheets-Sheet 1 [NVENTOR M y 936 H. E. MCCRERY 2,042,156

TAMPER FOR CONCRETE ROAD FINISHING MACHINES Filed Dec. 29, 193;; 4 Sheets-Sheet 2 May 26, 1936.

H. E. M CRERY TAMPER FOR CONCRETE ROAD FINISHING MACHINES Filed Dec. 29, 1935 4 Sheets-Sheet 3.

Patented May 26, 1936 UNITED STATES PATENT OFFICE TAMPER FOR CONCRETE ROAD FINISHING MACHINES Harold E. McCrery, Pittsburgh, Pa., assignor to Blaw-Knox Company, Blawnox, Pa., :1. corporation of New Jersey Application December 29, 1933, Serial No. 704,396

6 Claims.

This invention relates to tampers for concrete road finishing machines. The tamper settles and compacts the mix or aggregate which is poured between forms onthe bed or foundation pre-.

tamper consists essentially of a wooden plank or the like resiliently supported on edge from the machine by a spring support at each end, the plank extending transversely of the road bed. Each spring support consists of a pyramided series of leaf springs similar to the well known carriage spring, the end of the transverse plank or other tamper member being supported from the central and thickest portion of the set of leaf springs.

In order to oscillate the tamper in an up and down direction, power to alternately raise and lower it is applied to it at some point near its middle. To prevent this power applying means from transmitting jar to the truck which carries the tamper, it is usual to employ weights, rotated about pivots which do not pass through their centers of gravity. The power for rotating the weights is generally derived from the same 35 engine or motor as propels the finishing machine along the road rails.

Concrete used in road construction consists of a mixture of particles of hard materials, such as stone, gravel and cement, with water. All of these materials are practically incompressible. Tamping does not compress them. It produces its compacting effect upon them by jarring them so that any particles which when poured rest against one another point or edge to face, turn known as road rails. A well known form of slightly and rest face to face. Whenthey do this,.

terious. As a consequence, the amount of tamping that may be employed advantageously with wet concrete is small, while with very dry concrete the amount required to secure best results may be very great.

It is not the violence of the blows of the tampers used in compacting concrete, but the frequency with which blows are repeated, that gives tamping its greatest efiiciency, and determines the time required to tamp a given mix sufficiently.

The amount of tamping that can be applied to a concrete road with the machines hitherto in use has been limited by the frequency of the blows struck by the tamping elements of those machines-usually about four or five blows per second in normal operation, (240 to 300 blows per minute). It being necessary to construct such roads at a reasonable rate of speed,-from 500 to 1200 feet of road length per day, it was necessary to use concrete of a consistency that could be spread, tamped and finished at such rates, although it was well known that concrete containing less water would give better concrete if it could be placed properly.

The present invention relates to the tamping elements of a finishing machine, the construction being such that the blows may be speeded up to from 60 to 90 per second, (3600 to 5400 per minute), thus rendering the machine many times as effective in tamping relatively dry concrete as the tampers hitherto in use on such machines. While the desirability of such high frequency operation has been known for a long time, difficulties have been encountered in applying the principle of this rapid tamping in the construction of concrete roads; and although trials have been made of apparatus designed to give the high frequency jarring action, such apparatus has not been completely successful. The high speeds involved rack the tamper, and the strains brought about by the high speed drive impart excessive vibration to the finishing machine as a whole. The speed which it has been possible to maintain through day in and day out operation has been limited by the design of the structure of the tamper.

One object of my invention is to overcome the destructive action of the high speed tamping on the finishing machine or other carriage serving as a mounting for the tamper, at the same time making the stresses imparted to the tamper less injurious to the tamper itself. A further object is to provide a construction equipped with such vin position by means of the lock nuts driving means that the tamper may be driven at the desired high speed without shortening the life of the apparatus unduly.

I provide a tamping member which is comparatively light and yet so constructed as to be relatively rigid and remarkably resistant to deformation. I furthermore space devices along the tamping member for imparting rapid oscillations thereto, and give a nice balance to the structure by proper spacing of the devices and by connecting the devices so as to be driven in the same phase.

The present preferred embodiment of my improved construction is illustrated in the drawings, in which Figure 1 is a view in elevation of a portion of a concrete road-finishing machinewith the tamper extending transversely with respect to the road bed;

Figure 2 is a plan view of the mechanism shown in Figure 1;

Figure 3 is a view in end elevation of the resil lent spring suspension and adjusting mechanism therefor at the right-hand end of the mechanism .shown in Figure 1 (the driving mechanism including the prime mover being omitted to avoid confusing the view);

Figure 4 is avertical sectional view on line IV-IV of Figure 1;

Figure 5 is a vertical sectional view through a rotor and the casing therefor, together with the adjacent portion of the tamping member;

Figure 6 is a vertical sectional view on line VIVI of Figure 5;

Figure 7 is an end view in elevation of a modifled design of flexible driving connections between the motor and the drive shaft of a rotor;

and

Figure 8 is a view in side elevation of the mechanism shown in Figure '7.

An elongated tamper 4 extends transversely of the road bed. It is constructed of sheet metal stiffened by curved ribs 5 welded to the sheet at intervals, especially at the points where the rotors, hereinafter described,.are attached. The concave surface presented by the trough-shaped member 4 is of advantage in settling the material and finishing the road with a smooth surface. The bowed sheet of metal is exceptionally rigid along its long dimension or transversely of the road and at the same time its total weight is reduced to a minimum.

The tamping member 4 is suspended from the frame! of the finishing machine by means of upright members 8 at each end of the tamping member. These upright members 8 are secured at each end of an inverted T-beam 9 which forms a rigid backing for the tamping member 4. The bowed sheet of metal which directly engages the aggregate is secured to the horizontal flange of the inverted T-beam 9 at each one of the ribs 5 by studs l0 and nuts H (see Figures 4 and 5). Preferably, a plurality of nuts II are employed providing an adjustable mounting of the troughshaped sheet of metal beneath the T-beam 9, whereby the distance of the trough from the bottom of the beam 9 may be varied and then looked By making such an adjustment, it is possible to spring the trough a sufiicient amount to impart the desired crown to the road under construction. The ribs are provided at such intervals as may be necessary to secure rigidity between the T-beam 9 and the trough when the nuts II are tightened. when thus positioned by the studs It) with respect to the T-beam 9, an exceptionally rigid structure is provid d for the total length involved.

The trough 4 is somewhat shorter than the distance between the road rails I! so that it can descend down between them and engage aggregate with its convex bottom below the tops of the road rails. The raising and lowering mechanism shown at the two ends of Figure 1 and in Figure 3 is of a well known type. This mechanism makes it possible to position the trough 4 below the tops of the road rails, at-the level of the rails, or in elevated position above the rails. rights 8 are secured by bolts M at their upper ends to sets of leaf springs l5. At each end of the longest (and, therefore, the lowermost) spring is a pivot l1. vertically slidable in a slot I. in a link l9. The upper ends of the links I! are pivoted to bell cranks 2|) and 2| which are pivoted at 22 and 23 to a supplemental frame "la carried on the main frame I.

The slots i8 permit greater amplitude of the vertical oscillations of the tamping member than the stiffness of the springs l5 would ordinarily permit. At the same time, any turning movement of the bell cranks 20 and 2| with respect to the frame 1 brings about a raising or lowering of thelinks l9, thus changing in general the elevation of the tamping member.

I have provided improved means for rocking the bell crank levers 20 and 2| simultaneously. A lever 25 is pivoted to the frame 1 at 26 and carries a short rock arm 21 which is connected by an adjustable link 28 to one arm of a bell crank 20. A shaft 3| extends transversely of the roadfinishing machine and is keyed to both the crank 3|) shown in Fig. 3 and the crank 3|) at the other end of the machine so as to cause the two raising and lowering mechanisms at the two ends of the machine to function in unison. Rocking of the bell crank 30 transmits rocking motion to the bell cranks 20 and 2| through a rod 32 and a connecting link 33. Thus, by moving the lever 25 in one direction, the trough is raised, and by moving it in the other direction, the trough is lowered. A ratchet 34 is provided to hold the lever 25 in any desired position.

The tamper 4 is oscillated by means of rotors 35 mounted thereon at spaced intervals. The rotors are mounted on the tamper as illustrated in Figure 4, each of the rotors being secured to a plate 36 which is welded to the T-beam 9 and also to vertical plates 31 which are welded to each side of the web of the T beam.

The construction of'the rotors 35 is illustrated more in detail in Figures 5 and 6. Each of the rotors is enclosed in a casing 38 having a removable head 39 at one end which is secured to the casing by bolts 40. Inside of the casing is a rotor shaft 4| mounted adjacent its ends in roller bearings 42 and 43. Secured to the center of the shaft 4| is an eccentrically mounted weight 44 having a cylindrical insert 45 which may be moved toward or away from the axis of the shaft The upin a threaded opening 46 by means of a socket ing 38 are provided with threaded openings 49 and 50, respectively. A fitting 5| is threaded into the opening 50. The fitting receives one end of a pipe 52, inside of which is a flexible shaft 53 which connects the rotor shafts ll of the two rotors 35 so that they rotate in unison. The end of the flexible shaft 53 fits into an opening 54 formed in the right-hand end of the shaft ll, the two shafts being secured by a pin 55. In Figure 5, the flexible shaft 53 is connected to one end of the rotor shaft 4|, it being assumed that the rotor shown in this figure is the left-hand rotor shown in Figure 1 and that only two rotors, as shown in Figure 1, are employed for oscillating the tamper. If, however, the tamper is long enough to warrant it, more than two rotors may be employed, in which case the middle rotor, or rotors, would have flexible shafts corresponding to the shaft 53 of Figure 5 connected to each end of the rotor shafts.

The rotors are spaced at such intervals along the tamper as to cause it to move as a unit instead of setting up vibrations therein which would more or less distort the same. To this end, it is essential that the weights 44 of the rotors should be rotated in substantially the same phase. By the term in the same phase", I mean that the rotors are connected so that the weights on the shafts of the different rotors are at the top and bottom of their circular motions at the same time.

Preferably, as shown, the weights all rotate in the same direction. The motion of the tamping member therefore is not simply an up and down motion, but possesses a lateral component as well. The purpose is not to press the concrete, but to shake it. In action, the actual motion is very small,between and of an inch, the tamper being in continual contact with the concrete all along its bottom during the process. It is not desirable in this tamper to eliminate as far as possible all but vertical motion, as has been done in slower moving tampers for mechanical reasons.

The stresses set up in the tamper are at a minimum where each rotor is apportioned substantially the same mass to be raised and lowered thereby. Accordingly, I prefer to space the rotors along the tamper so that each vibrates a substantially Equal mass thereof. The rotors may be driven from the engine usually provided for driving the various mechanisms on the finishing machine. Where electric current is available, they may be driven by an electric motor, or they may be driven from any other source of power available.

However, as the improved tamper may do many times as much work upon the concrete in a given time than is possible with the older tampers, it should be supplied with more power, and I prefer to drive it by a separate engine or motor on that account, as well as because by doing so I can make the power transmission mechanism simpler and can also regulate the tamper speed without reference to the speed of propulsion of the machine along the road rails. I

One arrangement of driving connections for driving the rotors is illustrated in Figure 1. A gas engine 60 is provided with a drive sprocket 5| which is connected by a sprocket chain 62 to a sprocket 53 on a jack shaft 64 mounted at one end in bearings 65, the other end being connected to one of the rotor shafts. The shaft 64 is flexible so that the rotors may be driven irrespective of the elevation of the tamper. The engine 50 is mounted on the frame I of the finishing machine, whereas the tamper raising and lowering mechanism may be operated by the lever 25, as previously described.

In Figures 7 and 8, there is shown an alternative arrangement of driving connections for the rotors. In this modification, a grooved pulley 10 secured to the driving shaft of the engine drives a grooved pulley ll secured to a rotor shaft I2, the two pulleys being connected by a V-belt 13. A belt tightener 14 carrying an idler pulley I5 is provided to take care of the slack in the belt due to raising and lowering of the tamper with respect to the engine.

In order that the tamping mechanism may be thrown in and out of gear, a clutch I5 is provided intermediate the engine shaft and the sprocket 6| of Figure 1 or the pulley 10 of Figure 8. This clutch is actuated in the usual manner by a hand lever or the like.

With a construction such as disclosed herein, it has been found that the obstacles which formerly prevented the application of rapid tamping in the construction of concrete roads have been overcome, and that the high speeds necessary to 25 ings are to be avoided; the use of a flexible shaft, 30

such as disclosed herein at 53, does not involve such mechanical dlfflculties in exact alinement of rotors. This is particularly advantageous for avoid'ng to a large extent the wear and tear which had hitherto seemed a necessary conse- 35 quence of high speed drive. Moreover, by using a flexible shaft, vibration as a factor in causing excessive wear in the bearings is to a large extent eliminated. In other words, a vibrating rigid shaft is constantly flexing into misalinement with its bearings; but deflection of a flexible shaft does not have the same damaging results with regard to stress and wear in the bearings.

When the machine is running with the tamper raised and not in contact with the concrete, the only ways in which energy is dissipated are in friction of moving parts, and heating of the parts of the members due to their bending under the osci latory forces to wh ch they are subjected. Could these parts be made so strong that there would be no bending, these internal losses would be eliminated altogether, and it would take no power to run light, except that necessary to overcome friction and windage. However, at the rapid speed at which the tamper is run, bending cannot be eliminated altogether, or even approximately, without making the tamper excessively heavy. On the other hand, the heavier the trough, the greater its inertia as a whole. Consequent'y, if thetrough be unduly heavy, it will make it impossible to transmit a large amount of power to the concrete. Therefore, it is preferable to make the tamping member as a whole as light as possible without sacrifice of stiffness. The rotors are therefore so spaced as to subject the trough to a minimum of bending, and are run in unison, or synchronism, for the same purpose. In the preferred position they are shown as arranged to rotate on a common horizontal axis. They might rotate, each on its own horizontal axis at right angles to the axis shown, or each on an independent vertical axis, either one of which arrangements having the effect of tending to move the trough as a whole, rather than to transmit vibrations along it and to bend it between rotors. It is not essential to the invention that the tamping member have an up and down component to its motion, such as is produced by rotation of the weights in vertical planes. when it is in contact with the concrete all along its length, slight motion in a horizontal plane only, such as is produced by rotation of the weights in horizontal planes, is capable of contributing the necessary jar to cause the particles of concrete to rearrange themselves.

A further advantage of the construction disclosed herein is the fact that the frequency of oscillation can be controlled by the speed of the engine; and during trial tests the speed or frequency of vibration has been varied from 3600 to 5600 complete oscillations per minute.

While the moment of the rotating weights obviousIy cannot be adjusted, in the construction illustrated, unless rotation of the weights is arrested; nevertheless, changes in the speed of their rotation do vary the centrifugal forces. Therefore, ability to control engine speed in such a construction is practically the equivalent, under certain circumstances, of ability to adjust the weights while running, so far as the resulting efiect on the concrete is concerned.

While I have illustrated and described a preferred embodiment of my invention, it will be understood that the same is not restricted to the specific details of such preferred embodiment, but may be variously modified within the contemplation of the invention and under the scope of the following claims.

I claim:

l. Mechanism for tamping material such as cementitious mixes comprising a vehicle, an elongated material-engaging means including a stifiening beam resiliently supported from the vehicle,

a plurality of weights mounted at spaced points along said beam for eccentric rotation in vertical planes, each weight comprising a portion thereof shiftable radially relative to the remainder of the weight, and means for rotating said weights in substantially the same phase.

2. Mechanism for tamping material such as cementitious mixes comprising a relatively light beam, a sheet metal trough suspended beneath the beam in spaced relation thereto, means for resiliently supporting said beam in transverse relation to a road bed, a plurality of weights mounted at spaced points along said beam for eccentric rotation, means including stiffening ribs for the sheet metal trough connecting the trough to the beam at said spaced points, and means for rotating said eccentric weights insubstantially the same phase.

3. Mechanism for tamping material such as cementitious mixes comprising a relatively light beam, a work engaging member suspended beneath the beam of bowed or trough shaped sheet metal reinforced at spaced points by stiii'ening 5 ribs,'connections at said spaced points between said ribs and the beam, a plurality of weights mounted on the beam for eccentric rotation, and means for driving said weights including driving connections thereto ensuring rotation of all of 10 the weights in substantially the same phase.

4. In a road making machine, a tamping device comprising a beam and a trough shaped sheet metal member mounted beneath said beam in spaced relation thereto, the trough shaped 5 member'being positioned with its convex side down, a plurality of rotors secured at intervals to said beam, each of said rotors having a rotor shaft individual thereto and a weight fixed eccentrically thereon, a flexible shaft connected 20 to each rotor shaft, and means for driving said flexible shafts, said flexible shafts being so connected to the rotor shafts so as to rotate the weights in substantially the same phase.

5. Mechanism for tamping cementitious mixes 25 or the like comprising a rigid backing element, a work engaging trough secured beneath said backing element, means for resiliently supporting said backing element above the work, a plurality of weights eccentrically mounted on said backing 30 element at spaced points lengthwise thereof for rotation about longitudinal axes, said weights being arranged at such intervals along said element as to proportionately distribute the mass to be oscillated, and means for driving said 35 weights comprising flexible shafts uniting them for simultaneous rotation in substantially the same phase.

6. Mechanism for tamping material such as mixes for concrete roads comprising a tamper, means for resiliently supporting said tamper in transverse relation to a road bed, and means for oscillating said tamper as a whole in vertical and horizontal directions combined, said oscillating means comprising'a plurality of weights mounted at spaced points along the tamper for eccentric rotation, the axes of rotation extending lengthwise of the tamper, and means for rdtating said weights in substantially the same phase, said tamper comprising a beam and a work engaging element of outwardly bowed or trough shaped sheet metal mounted beneath said beam for adjustment toward and away from the beam.

HAROLD E. MCCRERY. 

